Posts Tagged mechanical design

[ARTICLE] Compliant lower limb exoskeletons: a comprehensive review on mechanical design principles – Full Text

Abstract

Exoskeleton technology has made significant advances during the last decade, resulting in a considerable variety of solutions for gait assistance and rehabilitation. The mechanical design of these devices is a crucial aspect that affects the efficiency and effectiveness of their interaction with the user. Recent developments have pointed towards compliant mechanisms and structures, due to their promising potential in terms of adaptability, safety, efficiency, and comfort. However, there still remain challenges to be solved before compliant lower limb exoskeletons can be deployed in real scenarios. In this review, we analysed 52 lower limb wearable exoskeletons, focusing on three main aspects of compliance: actuation, structure, and interface attachment components. We highlighted the drawbacks and advantages of the different solutions, and suggested a number of promising research lines. We also created and made available a set of data sheets that contain the technical characteristics of the reviewed devices, with the aim of providing researchers and end-users with an updated overview on the existing solutions.

Background

Robotic wearable exoskeletons1 have potential impact in several application domains, like industry [1], space [2] and healthcare [3]. In the healthcare sector, this technology is expected to contribute by reducing the clinical costs associated with the assistance and rehabilitation of people with neurological and age-related disorders [3456]. Research in this area is clearly shifting toward the inclusion of compliant elements (i.e. actuators, structure2, etc.) as a way to overcome the main drawbacks of rigid exoskeletons, in terms of adaptability, comfort, safety and efficiency [7].

Currently, there is a large variety of designs of lower limb compliant exoskeletons aimed at gait rehabilitation or assistance. However, there is a lack of detailed information about the mechanical components of these devices, which has been largely overlooked by previous reviews (e.g. [789]). These variety and lack of information makes it difficult for developers to identify which design choices are most important for a specific application, user’s need or pathology. For this reason, we aimed to bring together available literature into a comprehensive review focused on existing lower limb wearable exoskeletons that contain compliant elements in their design.

In this work, we refer to ‘compliant exoskeleton’ as a system that includes compliant properties derived from non-rigid actuation system and/or structure. Our review focused on three particular aspects: the actuation technology, the structure of the exoskeleton and the interface attachment components3.

We have gathered the mechanical and actuation characteristics of 52 devices into standardized data sheets (available at Additional file 1), to facilitate the process of comparison of the different solutions under a unified and homogeneous perspective. We consider that such a comprehensive summary will be vital to researchers and developers in search for an updated design reference.

Methodology

We applied the following search query on the Scopus database: TITLE-ABS-KEY(“actuat*” AND (“complian*” OR “elastic*” OR “soft”) AND (“exoskeleton*” OR “rehabilitat*” OR “orthotic*” OR “orthos*” OR (“wearable” AND “robot*”)) OR “exosuit” OR “exo-suit”), which returned 1131 studies. We excluded: publications focusing on upper limb robots; non-actuated compliant exoskeletons; solutions where compliance was achieved through control; studies that did not report any mechanical information on the robot; and studies not related to either assistance or rehabilitation. The above process resulted in a total of 105 publications, which covered 52 different lower limb exoskeletons.

To simplify and structure the information, we classified the compliant exoskeletons according to the mechanical component that results in their intrinsic compliant performance: (i) exoskeletons with compliant actuators (i.e. series elastic, variable stiffness and pneumatic actuators) and rigid structure; (ii) exoskeletons with soft structure (soft exoskeletons4) and rigid actuators; (iii) exoskeletons with compliant actuators and soft structure. The review describes the different design choices of the exoskeletons, i.e. actuation system, structure and interfacing attachment components to connect the actuators with the human body.

A glossary with the most commonly used terms in this article has been added at the end of the document. Some definitions have been readapted from the literature.

Results

As shown in Fig. 1, 85% of the reviewed articles (corresponding to 44 exoskeletons) used compliant actuators and a rigid structure. Soft exoskeletons represent 11% of the reviewed articles (6 exoskeletons). Two exoskeletons (4%) belong to the intersection of previous groups, this is, exoskeletons integrating both soft structure and compliant actuation5. We refer to the latter as “fully compliant exoskeletons”.

Fig. 1
Fig. 1

Classification of the 52 lower limb exoskeletons according to their compliant mechanical component

 

Continue —>  Compliant lower limb exoskeletons: a comprehensive review on mechanical design principles | Journal of NeuroEngineering and Rehabilitation | Full Text

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[Abstract + References] Development of Hand Exoskeleton Prototype for Assisted Rehabilitation – Conference paper

Abstract

The present work describes the design and construction of an exoskeleton prototype for hand rehabilitation. The device is designed for independent movements on each finger, considering the anthropometry of Mexican people and the rehabilitation paradigm. The stages for the prototype development are the design, mechanical characterization, position and orientation control, and exoskeleton assembly. As a result, the first prototype of exoskeleton for hand rehabilitation was obtained, thus, indicating the materials used in the different pieces and performing some physical tests for the validation of the mechanism.

References

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[ARTICLE] Development of a robotic device for post-stroke home tele-rehabilitation – Full Text

This work deals with the complex mechanical design task of converting a large pneumatic rehabilitation robot into an electric and compact system for in-home post-stroke therapies without losing performance. It presents the new HomeRehab robot that supports rehabilitation therapies in three dimensions with an adaptive controller that optimizes patient recovery. A preliminary usability test is also conducted to show that its performance resembles that found in RoboTherapist 2D commercial system designed for hospitals. The mechanical design of a novel and smart two-dimensional force sensor at the end-effector is also described.

According to the World Health Organization, by 2050, the number of persons over 65 years old will increase by 73% in the industrialized countries and by 207% worldwide.1 This segment of population is particularly prone to suffer a cerebrovascular accident or stroke, since the relative incidence of stroke doubles every decade after age 55. Stroke survivors immediately experience hemiparesis, resulting in impairment of extremities associated with diminished health-related quality of life.2 Rehabilitation can help hemiparetic patients to learn new ways of using and moving their weak arms and legs. It is also possible with immediate therapy that people who suffer from hemiparesis may eventually regain movement. However, reductions in healthcare reimbursement place constant demands on rehabilitation specialists to reduce the cost of care and improve productivity.3 Service providers have responded by shortening the length of patient hospitalization.4,5 Additionally, early home supported discharge of subacute stroke patients has been proved to have a significant impact on motor recovery after stroke although it requires some level of innovation of methods and tools for service delivery to really become a sustainable solution for the healthcare system.6,7 All these reasons support the necessity of in-home rehabilitation systems as the one proposed in this work.

Socially, chronic stroke patients can highly benefit from innovative approaches based on home rehabilitation therapy.8 Technological and scientifically, only a few commercial systems are currently available for in-home use (e.g. HandMentor™,9 ReJoyce,10 and ArmeoBoom from Hocoma), and their performances are not comparable to in-person therapies.11 Key challenges not addressed properly for home systems include features such as affordability, autonomy, and high performance. Only if all requirements are satisfied, it will be possible to encourage national health systems, insurance companies, and patients to apply such platforms.

This work is part of an ongoing project called HomeRehab that will develop a new tele-rehabilitation robotic system for delivering therapy to stroke patients at home. Instead, Technologies has a robotic system called RoboTherapist 2D (Figure 1) developed to provide rehabilitation to patients who suffer from stroke and/or other neurological disorders.12 Currently, the system, as the majority of commercial devices, is only designed to be used in hospitals and medical centers in collaboration with nurses and medical staff.13

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Figure 1. RoboTherapist 2D system from Instead Technologies.

HomeRehab aims to modify and adapt the system so it can be used at home by patients easily and supporting the premise of tele-rehabilitation.14 This article describes in detail the mechanical design of the new HomeRehab system that adapts the RoboTherapist 2D for in-home use by making it smaller, lighter, and cheaper, but maintaining its high performance. Additionally, the system includes a third degree-of-freedom (DOF) plus a novel low-cost force sensor that were not considered for the original platform, but they are very interesting features for a complete in-home solution. Another key feature of the whole system is that it integrates patient monitoring techniques using wearable devices to monitor the physiological state of the patient and modify exercises based on that information.

The following section briefly summarizes the main requirements considered to develop a successful device, and afterward in section “Mechanical design,” the mechanical design of the new system is described in detail. Section “Robot controller” presents the controller of the robot as well as the adaptive controller implemented for the rehabilitation therapies. Section “Usability pilot study” carries out a validation phase by conducting several tests and surveys to compare the usability of RoboTherapist 2D with HomeRehab, and last section gathers main conclusions. […]

 

Continue —>   Development of a robotic device for post-stroke home tele-rehabilitationAdvances in Mechanical Engineering – Iñaki Díaz, José María Catalan, Francisco Javier Badesa, Xabier Justo, Luis Daniel Lledo, Axier Ugartemendia, Jorge Juan Gil, Jorge Díez, Nicolás García-Aracil, 2018

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